1. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Nicholas R. Zeigler Lindsay N. Zack Neville J. Woolf Lucy M. Ziurys Department of Chemistry Department of Astronomy Steward Observatory Arizona Radio Observatory University of Arizona HCO + in the Helix Nebula

2. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Planetary Nebulae Glowing shell of gas and plasma formed by low to intermediate mass stars in their final stage of evolution Strong UV radiation field from central star Shapes and sizes vary

3. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Morphologies

4. June 21, 2013 68 th International Symposium on Molecular Spectroscopy The Helix Nebula Age: ~12,000 years Distance: ~200 pc Angular Size: ~1000 ” Very old Lots of dust and gas Atomic gas : H , N II, O I, C I Molecular gas: CO, H 2, Polyatomic molecules: C 3 H 2, H 2 CO (Tenenbaum et al 2009) Interesting structure Cometary globules

5. June 21, 2013 68 th International Symposium on Molecular Spectroscopy The Helix Nebula Age: ~12,000 years Distance: ~200 pc Angular Size: ~1000 ” Very old Lots of dust and gas Atomic gas : H , N II, O I, C I Molecular gas: CO, H 2, Polyatomic molecules: C 3 H 2, H 2 CO (Tenenbaum et al 2009) Interesting structure Cometary globules Taylor 1977

6. June 21, 2013 68 th International Symposium on Molecular Spectroscopy The Helix Nebula Age: ~12,000 years Distance: ~200 pc Angular Size: ~1000 ” Very old Lots of dust and gas Atomic gas : H , N II, O I, C I Molecular gas: CO, H 2, Polyatomic molecules: C 3 H 2, H 2 CO (Tenenbaum et al 2009) Interesting structure Cometary globules O’Dell et al. 2004

7. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Globules

8. June 21, 2013 68 th International Symposium on Molecular Spectroscopy CO (J = 2-1) Map of the Helix Young et al. 1999 Multiple Velocity Components

9. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Why HCO + ?  = 3.89 D High critical density (n cr ~ 10 5 cm -3 ) indicates that HCO + emission is present in dense gas around the Helix – CO:  = 0.11 D; n cr ~ 10 3 cm -3 Dense gas is shielding and can preserve molecules

10. June 21, 2013 68 th International Symposium on Molecular Spectroscopy HCO + Observations ARO 12m on Kitt Peak HCO + (J = 1-0) 89.18853 GHz Optimal project for new ALMA- type Band 3 receiver ( 84–116 GHz ) – T sys < 200 K – rms noise < 20 mK Map across entire Helix (~1000” x ~ 800”) KP 12m

11. June 21, 2013 68 th International Symposium on Molecular Spectroscopy 35″ spacing 129 positions Beam Size (70″) 70″ spacing 89 positions Integration time ~2-3 hours

12. June 21, 2013 68 th International Symposium on Molecular Spectroscopy HCO + Integrated Intensity Column densities: – Range: N tot ~ 1.4 × 10 11 – 2.4 × 10 12 cm -2 – Average: N tot ~ 4 × 10 11 cm -2 – Average f(HCO + /H 2 ) ~ 5.3 × 10 -8 cm -2

13. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Comparing Atomic and Molecular emission H2H2 Optical HCO + CO

14. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Velocity Partitions CO (Young et al 1999)HCO + (J=1-0)

15. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Velocity vs. Position Angle Young et al 1999 CO

16. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Velocity vs. Position Angle HCO +

17. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Velocity vs. Position Angle HCO +

18. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Red/Blue shift separated plots Red shiftBlue shift

19. June 21, 2013 68 th International Symposium on Molecular Spectroscopy H 2 Overlays -35 km/s-11 km/s O’Dell ModelSpeck, A. 2002

20. June 21, 2013 68 th International Symposium on Molecular Spectroscopy 3D Structure

21. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Summary The HCO + emission is coincident with the CO emission, indicating that dense gas exists throughout the Helix Molecular distribution corresponds with atomic emission, indicating that molecular material is ubiquitous. The model for the structure of the Helix has been improved.

22. June 21, 2013 68 th International Symposium on Molecular Spectroscopy Acknowledgements Funding NASA NSF Ziurys Group Matt Bucchino, Debbie Schmidt, DeWayne Halfen, Lucy Ziurys, Julie Anderson, Jessica Edwards, Jie Min, Gilles Adande, and Debbie Schmidt